Glass curtain wall is the “face project” of modern architecture. It makes high-rise buildings look transparent and fashionable, but many people find that the initial cost of installing glass curtain wall is much higher than that of ordinary brick wall or concrete wall. Why is this? In fact, from material selection to construction details, every link is pushing up the cost. Today, Zhongdong Curtain Wall will talk to you about why glass curtain wall is expensive?
1. Material cost: glass is not “ordinary glass”
The “glass” of glass curtain wall is completely different from the glass of our windows at home. Ordinary glass costs dozens of yuan per square meter, but the price of curtain wall glass may double or even dozens of times. The main reasons are:
1. High requirements for special treatment
Tempered glass: Curtain wall glass must use tempered glass (safety glass). Ordinary glass will break when hit, and falling from high altitude will cause death. The production of tempered glass requires high-temperature heating and rapid cooling, and the cost is 30%~50% higher than ordinary glass.
Laminated glass: To prevent the glass from falling after breaking, many curtain walls use laminated glass (a layer of PVB film is sandwiched between two layers of glass). For example, the glass ceiling of the atrium of the shopping mall will stick to the film and will not fall off even if it breaks. However, the film material and processing technology will increase the cost again.
Insulating glass: In order to soundproof and heat-insulate, curtain walls often use insulating glass (inert gas is filled between two layers of glass). The production line of this kind of glass is complex, the gas filling and sealing requirements are high, and the price is more than twice that of single-layer glass.
2. Coating and energy-saving technology
LowE glass: Many high-end curtain walls use LowE glass (low-emissivity coated glass), which reflects sunlight heat in summer and prevents indoor heat loss in winter. This kind of glass requires vacuum coating technology, and the cost is 50%~100% higher than ordinary glass.
Double silver/triple silver coating: The higher-end coating can even automatically adjust the light transmittance according to the light, but the price of this kind of glass may exceed 1,000 yuan per square meter.
3. Metal frames are not cheap
The skeleton of glass curtain walls is usually aluminum alloy profiles, but ordinary aluminum alloys are not strong enough, so high-strength models must be used. This type of profile requires a special extrusion process, and the price is 20%-30% higher than ordinary aluminum.
The surface of the frame must also be fluorocarbon sprayed or anodized to prevent rust and fading. For example, fluorocarbon spraying requires a multi-layer baking process, and the processing fee for one ton of aluminum profiles may increase by several thousand yuan.
2. Design cost: It is not just a random drawing that can be used
The design of glass curtain walls is much more complicated than ordinary walls. It must be beautiful, wind-resistant and shock-resistant, and thermal expansion and contraction must be considered. The size and installation method of each piece of glass must be accurately calculated.
1. Customized design
Ordinary brick walls can be constructed in a standardized manner, but glass curtain walls are “tailor-made” for almost every building. Curved, special-shaped, and oversized glass panels… These special designs require special modeling and force analysis, and the design fee may account for 5%~10% of the total cost.
2. Structural calculations are both brain-burning and expensive
Curtain walls have to withstand multiple pressures such as wind, earthquakes, and temperature deformation. For example, coastal high-rise buildings must be designed according to the typhoon wind pressure that occurs once in a hundred years, which requires complex structural calculations and wind tunnel experiments. These analyses must be completed by professional engineers, and the labor cost is hundreds to thousands of yuan per hour.
3. The details of the glass curtain wall nodes are expensive in the “invisible places”
The connection between the glass and the frame, the drainage channel, the expansion joint, and other detailed designs directly determine whether the curtain wall leaks or falls off. For example, a hidden drainage system may require dozens of additional parts, and each part must be molded and produced separately.
3. Construction cost: high-altitude operations are like “walking on a tightrope”
The installation of glass curtain walls is extremely difficult, especially for super-high-rise buildings. Workers hang hundreds of meters high to install glass, and the safety and precision requirements directly increase the cost.
1. Expensive labor costs
Ordinary construction workers earn 200 to 300 yuan a day, but curtain wall installers need high-altitude work permits, welding permits, etc., and their wages may double (400 to 500 yuan a day). If it is a foreign project, skilled workers may even earn more than 2,000 yuan a day.
2. Lifting equipment costs money
Installing glass curtain walls requires equipment such as tower cranes, elevators, and suction cup hoists. For example, the monthly rent of a high-rise tower crane may exceed 100,000 yuan, and a set of suction cup hoists may cost hundreds of thousands. If you encounter special-shaped glass, you have to customize special fixtures.
3. Long construction period
Ordinary brick walls can be built in a few days, but curtain wall installation may take several months. The longer the construction period, the higher the equipment rental, labor, and management costs. For example, for a 50-story building, the curtain wall installation may take more than half a year.
4. Safety measures cannot be saved
For high-altitude operations, scaffolding, safety nets, and high insurance must be purchased. For example, the insurance cost of a curtain wall project of a building may exceed one million yuan.
4. Transportation and warehousing: Glass is more delicate than tofu
The transportation and storage costs of glass curtain wall materials are often overlooked, but they are actually very expensive.
1. Easy to break during transportation
Glass is a brittle material. It must be wrapped in wooden boxes + foam layers during transportation, and even an air cushion car must be rented for shock absorption. For example, a 3m × 5m large glass may cost tens of thousands of yuan to transport from the factory to the construction site.
2. High storage requirements
Glass cannot be piled in the open air. It is afraid of rain and bumps. It is necessary to rent a warehouse with moisture-proof facilities. Aluminum profiles should also avoid extrusion and deformation, which takes up a lot of space. The rent of warehouses in first-tier cities is dozens of yuan per square meter per month, and it costs a lot of money to save for a few months.
5. Inspection and acceptance: pass five levels and cut six generals
The glass curtain wall cannot be used directly after installation. It must pass a lot of inspections, and these links are all burning money.
1. Performance testing
Wind pressure resistance, air tightness, and water tightness testing require the rental of large equipment. For example, when doing a water test, a high-pressure water pump is used to simulate a rainstorm. One test may consume hundreds of tons of water, plus labor and equipment costs, easily exceeding 10,000 yuan.
2. Material inspection
All materials (glass, glue, aluminum) must be sampled and sent to a third-party laboratory for testing. A test report costs several thousand yuan, and the full project test may cost more than 100,000 yuan.
